Boil pasta in 4-5 cups water.
In a separate pot, mix tomato sauce, bell peppers, corn, and beans, and cook on medium heat.
Note: a simple tomato pasta sauce is best--try to get one without too many Italian herbs (the spices will give it the "Mexi" flavor).
Add cumin powder and crushed red pepper--no need to measure, just eyeball it and adjust for how spicy you want it to be.
When pasta is done, drain (do not rinse) and return to the pot. Pour the sauce mixture into the macaroni, stir, and continue cooking. Use enough sauce to mix well with the macaroni but without any excess (it's not supposed to be "saucy" or soupy, so use less sauce than usual with this pasta). Cook until sauce and macaroni are hot.
Add cracked black pepper to taste, and shred nacho "cheese" over top if desired.
My mom always used to make this with our chili leftovers, but I've found it works just as well with the pasta sauce. (You can definitely try it with leftover chili too!)